1. Field of the Invention
The present invention relates to a rotary clutch device and a sheet feeder using the same. The present invention also relates to an image forming apparatus such as a laser printer, a copier, or a facsimile machine.
2. Background Art
A rotary clutch device provided in a sheet feeder of a laser printer is known in which a cam body having an engagement step on its outer circumferential surface is formed integrally with a tooth-partially-lacking gear that is linked to a D-shaped sheet feed roller. An engagement lever is provided so as to be engageable with and disengageable from the engagement step. When the mesh between the tooth-partially-lacking gear and a drive gear is canceled, the engagement lever engages the engagement step, whereby the tooth-partially-lacking gear and the sheet feed roller are stopped (e.g., JP-A-11-190410).
The engagement lever is operated intermittently with prescribed timing by an actuator such as a solenoid. An urging spring for imparting initial rotation force to the tooth-partially-lacking gear to cause the tooth-partially-lacking gear to mesh with the gear portion of the drive gear when an engagement nail located at the tip of the engagement lever is disengaged from the engagement step is connected to the tooth-partially-lacking gear. Therefore, immediately after the disengagement of the engagement lever from the engagement step, the cam body that is integral with the tooth-partially-lacking gear is rotated by the urging spring. The engagement lever is then returned to the original position due to the intermittent operation of the solenoid and hence the engagement nail of the engagement lever touches the outer circumferential surface of the cam body. At this time, an impact sound (a click) that occurs when the engagement nail of the engagement lever collides with the outer circumferential surface of the cam body.
In the technique disclosed in JP-A-11-190410, to reduce the impact sound, a cam release surface is formed, as part of the outer circumferential surface of the cam body, upstream of the engagement step in the rotation direction and a cam recovery surface is formed upstream of and adjacent to the cam release surface in such a manner that the radius (i.e., height) of the cam recovery surface is set laser than that of the cam release surface.
In the technique disclosed in JP-A-11-190410, by virtue of the above structure, the impact sound that occurs when the engagement nail touches the outer circumferential surface of the cam body approximately perpendicularly. However, the impact sound (a click) that occurs when the engagement nail of the engagement lever engages with the engagement step of the cam body that is given initial rotation force by the urging spring after the non-tooth portion of the tooth-partially-lacking gear is opposed to the drive gear and hence the mesh between the tooth-partially-lacking gear and the drive gear is canceled cannot be eliminated.